Decaying Reinforced Autoclaved Aerated Concrete in our NHS hospital roofs: Disclosed engineers’ reports and suppression

Dr Minh Alexander retired consultant psychiatrist 1 December 2022

This is a post to share engineers’ reports and related documents on NHS buildings that are at risk due to unsafe roofs.

It also feedbacks about NHS trusts which have failed or refused to disclose such information, in a context of minimisation by NHS England.

The NHS has always been underfunded, and building hospitals is a complicated business, with a history of good intentions followed by misfires.

Decades ago, some NHS hospitals were built quickly on the cheap, with central government oversight – the “Best Buy” hospitals, which were offered with the slogan “Two for the price of one!”.

East Anglia was the most enthusiastic adopter of the model.

Simple construction techniques included the use of limited-life Reinforced Autoclaved Aerated Concrete (RAAC) beams in roofs.

RAAC roofs were often flat, resulting in later problems with water ingress.

 Reinforced Autoclaved Aerated Concrete  

RAAC was developed in Sweden a century ago.  

It is composed of bubble-filled concrete, without coarse aggregate, which is usually embedded with metal reinforcements.  

The material is lighter, and insulates better, but it is less strong.  

“Compressive strength is significantly lower than traditional concrete at 2-5N/mm², as are related flexural, shear, and tensile strengths. Elasticity and creep are substantially inferior to traditional concrete due to the aerated nature and lack of coarse aggregate, which are reflected in large observed long-term deflections. [Bending]”  

RAAC also does not prevent corrosion of the embedded metal components as effectively as normal concrete.  

“…aerated RAAC’s vulnerability to moisture ingress means any reinforcement lacking sufficient protection becomes ultra liable to corrosion.”  

To compensate for this, in some RAAC beams, the metal elements were coated with bituminous material.   It has been found that this protective coating was not always properly applied.  

Surveys of failing RAAC roofs on school buildings have shown that a lot of the damage has related to water ingress,  resulting in corrosion of metal reinforcements, and loosening of the metal reinforcements from surrounding concrete.  

A worry is that such corrosion may NOT be visible on inspection:  

“Not all defects are visible … panels which appear to be in a good condition may conceal hidden defects which could present a risk to the integrity of the panels,” it said. “The corrosion of reinforcement could lead to large pieces of RAAC falling which presents a risk to occupants.”  

It has also been reported that there are variations in RAAC material, which may create additional unpredictability.    

Problems with RAAC roofs were evident by the 1980s:

“By the 1980s, RAAC roof planks installed in the 1960s had begun to fail. Subsequent case studies revealed significant underlying issues with the RAAC roof planks. The steel reinforcement was often insufficiently covered, allowing corrosion to occur. Many roof planks had a high span to depth ratio, meaning that they did not have the suitable capacity to span between bearing points. Often, the steel reinforcement did not extend throughout the complete length of the product and contained an inadequate number of welded crossbars.”

RAAC beams bend and may disrupt water proofing materials as they warp. Water ingress by this route, or other routes, may pose an added threat to the beams. Some beams were cut to fit particular sites, which would have removed important, extra metal reinforcements located at the ends of the beams and compromised their load bearing capacity. Harsh weather can also pose a threat to RAAC roofs. For example, snowfall can push RAAC roofs to their limit and this has to be factored into the risk management.

Worryingly, in August this year, Collaborative Reporting for Safer Structures UK (CROSS-UK) reported that RAAC beams had been found in the pitched roof a hospital built in the 1990s.

Who knows how many more exist?

And government guidance on identifying RAAC roofs only tells public bodies to look at buildings constructed up to the 1980s:

“RAAC is a lightweight, ‘bubbly’ form of concrete that was commonly used in school and other buildings from the mid-1960s to the mid-1980s.”[my emphasis]

It is thought that the safe life span for RAAC structures is about thirty years.

Some NHS hospitals have RAAC roofs which are known to exceed this 30 year timescale.

Trust board papers by an affected NHS trusts, Queen Elizabeth Hospital King’s Lynn NHSFT (QEHKL), asserted in February 2020 that the life span was even shorter – 25 years.

Consistent with this, QEHKL trust board papers indicate that the problem of the RAAC roofs has been on QEHKL’s risk register since May 2006 – twenty five years after the hospital was built.

An October 2021 report commissioned by NHS Property Services proposed these measures for managing RAAC roofs:


To help prolong the life of RAAC panels, the following rules should be adopted generally. A structural engineer should be consulted if the following cannot be complied with:

  • No additional loads to be applied to any RAAC panels.
  • No new fixings should be installed to the panels
  • No additional penetrations should be formed through the RAAC panels without a review from a structural engineer


The following should be put in place as operational procedures:

  • Where standing water is present on the roof, introduce robust pumping arrangements to discharge excessive quantities of water.
  • Snow build up on the roof should not be allowed to generally exceed 200mm. When removing snow, snow should not be piled in any location to height of greater than 300mm.
  • If snow does build up greater than 300mm, all accommodation below should be closed to access until the snow has been clear and panels re-assessed by a structural engineer.
  • Maintain robust roof permit system to control access to the roof and to inform personnel of restrictions

No roof maintenance should exceed the design loadings of 0.6kN/m2.”

Not all RAAC beams in NHS buildings have been surveyed due to problems of access, which makes risk assessment and management more difficult.

Some trusts have been forced into elaborate risk management arrangements, with frequent checks, physical propping of the roofs and full or partial decanting of some buildings.

Queen Elizabeth Hospital King’s Lynn NHSFT had to evacuate a theatre complex on an emergency basis this July, because of ceiling movement.

Local MP Liz Truss spoke about the problems at King’s Lynn during the recent Tory leadership race, but had reportedly ignored concerns for years.

At some NHS trusts, staff have been issued with guidance on signs of deterioration that should be reported.

But RAAC beams can fail suddenly and with little warning.

The 2018 index case of a school roof collapse, which led to a recent national alert about RAAC, occurred within 24 hours of the first signs:

“There were signs of structural stress on Friday evening and the collapse occurred last evening (Saturday)”

The government has not given the NHS enough money to address these risks promptly, and a replacement programme for the RAAC roofs is not scheduled for completion until 2035.   

In September the Lib Dems shared an FOI request to NHS England which revealed that there were 32 NHS buildings which had RAAC roofs:

 Number of buildings with RAAC roofs
Queen Elizabeth NHS FT4 (Kings Lynn)
West Suffolk NHS Foundation Trust2
James Paget University Hospitals NHS Foundation Trust1
North West Anglia NHS Foundation Trust2 (Hinchingbrooke Hospital) 1 (Stamford Hospital)
Mid and South Essex NHS FT1 (Broomfield)
Airedale NHS Foundation Trust1
Liverpool University NHS FT1 (Aintree)
Mid Cheshire Hospitals NHS FT4 (Leighton)
Blackpool Teaching Hospitals NHS FT2
Countess of Chester NHS FT1
University Hospital Southampton NHS FT1
Frimley Health NHS FT1 (Frimley Park)
Midlands Partnership NHS FT1 (Haywood)
Doncaster and Bassetlaw NHS FT2 (Bassetlaw)
Worcestershire Acute Hospitals NHS Trust1 (Kidderminster)
York Teaching Hospital NHS FT1 (Scarborough)
East Lancashire Hospitals NHS Trust1 (Royal Blackburn)
Northern Care Alliance1 (Royal Oldham) 1 (Salford)
NHS Trust total30
NHS Property Services1 Haverhill
 1 Warren Farm
NHS Property Services total2

NHS England advised on 28 October 2022 that this may not represent the full extent of NHS buildings affected by RAAC issues, and that effectively, no one knows how many more buildings need remediation.

“The safety of our people within our hospitals is of paramount importance to the NHS. On learning of the issues surrounding reinforced autoclaved aerated concrete (RAAC) beams, NHS England wrote out to all organisations in 2019-20, asking them to assess their buildings for RAAC. The result of this was the instigation of the national RAAC programme.  

Proactive steps are being taken to ensure that all RAAC in the NHS is identified and subsequently eradicated; the list above represents our current understanding of RAAC across the NHS.  

At this time, we cannot state that this is the final list of all instances of the material across the NHS however we have a clear process for tracking and mitigating RAAC if/as/when it occurs.” [my emphasis]

Contrasting with this tone of concern, the Eastern Daily Press reported in August 2021 on FOI request which showed that NHS England criticised the CEO of Queen Elizabeth Kings Lynn NHS Foundation Trust for being “sensationalist” about the RAAC risks.   

To obtain more detailed information on the risks, I asked affected NHS trusts and NHS Property Services for engineers’ reports and risk management documents.

Several trusts did not respond at all, or gave limited responses, which may reflect discouraging attitudes by NHS England and the Department of Health.

Others have upheld the public interest and shared information more transparently.

The data reveals a story of chronic anxiety, disruption and sometimes desperate making do.

It also shows that affected NHS trusts are painfully aware of not just the risks to people, but the likely legal, regulatory and health and safety blowback if the roofs collapse.

The data shared, whether in full or only partially, puts to shame NHS England’s unsupportive comments last year about the QEHKL then chief executive’s advocacy for her service.

She has since left the NHS, after forty years.

Local people continue to campaign.

See @save_lynn

And see the Westminster petition to prioritise for a new hospital for King’s Lynn & West Norfolk (now closed):

The information shared by affected trusts – or details of their lack of response – are listed below in the appendix.


York and Scarborough Teaching Hospitals NHS Foundation Trust

This trust provided one of the most detailed and transparent responses.

This gives a helpful comparator to the responses by trusts which were less transparent, showing what will have been omitted by these trusts.

The trust disclosed the following documents:

Structural report 20 December 2021

Workplace risk assessment 23 June 2022

Risk review of affected labs May 2022

RAAC roof weekly checklist form

Action plan June 2022

Poster for staff by Estates, raising awareness of warning signs of structural failure

Blackpool Teaching Hospitals NHS Foundation Trust

This trust also answered transparently and also disclosed the following documents:

Structural report 20 December 2019

Structural report 9 January 2020

Structural report 10 March 2020

Structural report 5 March 2021

Structural report 11 January 2022

The trust gave the following account of its risk management:

“The Trust has made safe the RAAC units in the laundry by providing a fail safe supporting structure. In line with guidance and initial evaluation by the approved structural engineers these are now inspected on an annual basis, The planks are not above patient or public areas, and as they are independently supported no progressive deterioration can be expected. Consequently, no special evacuation plans over and above a standard space evacuation for fire is envisaged, and the area would be re-inspected by engineers in the event of any detectable failure or deterioration of a unit.

The Units on Phase 4 roof are immediately above medical records storage. Each unit is secured between steel supports; therefore no progressive collapse is anticipated. As with the laundry the units are inspected annually, and currently all are in good condition. Additional investigation and evaluation is being undertaken in November. The roof therefore has a low risk score of 2 and consequently no special evacuation plans over and above a standard space evacuation for fire is envisaged, and the area would be re-inspected by engineers in the event of any detectable.”

Queen Elizabeth Kings Lynn NHS Foundation Trust

The trust has had the highest profile with regards to RAAC roof problems.

It was opened in 1980. The site weas mostly constructed with RAAC roofs.

NHS England’s above disparaging comments about the trust’s external comms seems, unsurprisingly, to have dampened the trust’s willingness to reveal details.

The trust has not provided engineers’ reports as requested, with no explanation, and has disclosed only this summary:

“Rolling programme of maintenance and failsafe installation

79% of the hospital buildings have RAAC planks that need monitoring and emergency repairs carried out on a rolling basis. We have a dedicated team of surveyors and technicians who survey the buildings and identify where support props and failsafes are needed to reduce the risk of plank failures in the roof and maximise safety.

In 2021/22, with £20.6m national capital funding we opened new Endoscopy and Outpatient Units to create the necessary theatre and ward decant space for a three-year rolling failsafe programme.

The first year of an £80m three-year programme is currently underway to install failsafes across the first floor of the hospital. The investment maximises safety and does not create additional ward space or capacity.

Evacuation plan in the event of RAAC failure

We have robust plans in place in the event of RAAC failure and these are tested regularly. This includes the East of England RAAC response plan and a smart evacuation system (which is recommended by NHS England in the East of England for implementation across all acute and community providers in the region). There is also an overarching Trust-wide evacuation plan which covers all eventualities.

Appropriate training has taken place and several exercises have been undertaken to test our response to a RAAC emergency. Learnings from these exercises have been used to further strengthen our plans.”

Although the trust has withheld engineers’ reports, there is a continuous summarised narrative in “Significant Risk” reports in the trust board papers.

Risk has been graded at 20 since 2019 (Likely catastrophic harm).

The Board papers also show that the RAAC roofs have been an open item on the trust risk register since May 2006:

The trust has benchmarked with other affected trusts and concluded that it was more badly affected than comparators such as Hinchingbrooke Hospital and James Paget Hospital:

In April 2022 the trust reported:

“We believe we are the most propped hospital in the country with 1,528 steel and timber support props in 56 areas of the hospital – almost three times more props than beds.”

By October 2022 the number of props had mushroomed:

Roof at crumbling hospital serving PM Liz Truss’s constituents is being held up by 2,500 props

There was a deeply concerning incident in July of this year when theatres had to be evacuated after movement was noticed in the ceiling above a theatre complex.

A hospital spokesperson, understandably, commented:

“This demonstrates once again that our hospital is unfit for purpose and the need for an urgent announcement about the desperately needed funding for a new QEH, recognising the impact on patient and staff experience and the operational running of our hospital.”

It beggars belief that a hospital that is incredibly stressed by COVID19 and all the other ills that beset the NHS, has to also juggle emergency evacuations of critical areas because of unpredictably failing infrastructure.

Frimley Health NHS Foundation Trust

Frimley claimed that it could not disclose the requested material because it is intended for future publication.

It has not answered questions about the purported future publication.

The construction of the Frimley site, under the “Best Buy” scheme, was originally monitored by the Department of Health.

Countess of Chester

The trust has failed to respond at all despite chasers.

Mid and South Essex NHS Foundation

Has not responded at all despite reminders.

Northern Care Alliance NHS Foundation Trust

The trust disclosed engineer’s reports:

Structural report Salford June 2022

Structural report Oldham July 2022 

In terms of documents on risk management, the trust stated on 21 October 2022:

“The Trust do not have an over-arching documented plan or protocol available. Work is still on-going to develop these kind of plans.”

Worcestershire Acute Hospitals NHS Trust

The trust has disclosed an engineer’s report:

Structural report August 2021

It gave this account of risk management:

“We can confirm that in line with the following report points, we undertook the following actions:

6.2- the first floor of A block was cordoned off
6.3- immediate mitigation of temporary steel props to underside of ceiling 6.5- we are currently undertaking a programme of works to replace the roof

This work has been funded by the National RAAC Replacement scheme and is regularly monitored by them.”

North West Anglia NHS Foundation Trust

The roof at Hinchingbrooke Hospital, run by the trust, is a well known example of the RAAC roof problems.

The trust has issued a blanket refusal to disclose any engineers’ reports on spurious grounds of “commercial interest”:

“Following a detailed review of both your initial and subsequent request, North West Anglia NHS Foundation Trust (the Trust) is withholding the engineers’ reports. It is the Trust’s view that this information is exempt under Section 43 (Trade secrets and prejudice to commercial interests).”

The trust has disclosed the following documents:

Datix Risk Assessment updated 24 Nov 2022 by Paul Denton Assoc Director of Governance and Risk

Risk action plan updated 26 October 2022

Emergency evacuation plan

Importantly, it is noted in these documents that not all the RAAC beams have been surveyed yet due to access problems.

The trust has identified the following as risks:

A published trust business case of July 2021 on affected main theatres gives additional information.

East Lancashire Hospitals NHS Trust

The trust has refused to disclose engineers’ reports claiming a spurious exemption of third party information:

“The full report is third party data therefore the Trust cannot disclose.”

The trust has disclosed only a fragment from a report, with no indication of date.

The trust has disclosed partial material from Quarter (3) 2022/23 which shows that there are between 300 to 500 RAAC panels in its buildings and 25% have yet to be surveyed.

The trust reported on 22 November 2022 that the affected areas have decanted and mothballed:

“The affected areas have been decanted and it has now become a restricted access construction site. Programme of works to remove the roof panels has commenced. There is no risk to patients, staff or the general public.”

Southampton University Hospital NHS Trust

The trust has not provided a response despite being reminded.

Midlands Partnership NHS Foundation Trust

The trust disclosed these engineer’s reports:

Structural report 28 January 2020

Stuctural report 17 December 2021

It advised on 27 October 2022 that props had been required and that the affected area had been decanted:

“Following a survey in February issues in three locations resulted in acro props being installed. Due to this the services were unable to safely access the day case unit, orthotics and out of hours nursing. Services were temporarily stood down and have now been fully decanted. The section of the Hospital with RAAC planks is now locked off and access managed and restricted to facilities and estates for the purposes of surveying and monitoring whilst the Trust works through the business case process for the replacement of the building.”

West Suffolk NHS Foundation Trust

The trust has disclosed an engineer’s report and details of risk mitigation:

Structural report March 2021

Risk mitigation details

Doncaster and Bassetlaw Teaching Hospitals NHS Foundation Trust

The trust has disclosed an engineer’s report and a diagram of RAAC panels surveyed:

Structural report 22 October 2021

Diagram of RAAC panels surveyed

Liverpool University Hospitals NHS Foundation Trust

The trust disclosed only an extract from an engineer’s report:

Extract from report by Curtins engineers

The trust gave this strange response to the request for details of risk management:

In accordance with Regulation 12(4)(a) of the EIR, we can confirm that the Trust does not record/collate the above information.”

James Paget University Hospital NHS Foundation Trust

The trust has not responded at all despite being reminded.

Mid Cheshire Hospitals NHS Foundation Trust

The trust refused to disclose any information at all, pleading that it would require too much work to collate the documents:

In order to comply with your request it would require an extensive manual review and cross reference of a vast number of reports, plans and protocols. In addition, some of this information is not held in a document format and would require additional work to collate it.”

If true, this is not reassuring evidence that it is on top of matters.

Mid Cheshire has now delayed its response to a request for internal review until 5 January 2023.

Could that be political water treading, pending an NHS England communication of some sort?

NHS Property Services

NHS Property Services did not answer at all despite being reminded.

However, a report on a property that it manages, Warren Farm Health Centre, which has an RAAC roof is in the public domain:

WARREN FARM HEALTH CENTRE Monitoring and Remedial Strategy

One thought on “Decaying Reinforced Autoclaved Aerated Concrete in our NHS hospital roofs: Disclosed engineers’ reports and suppression

  1. I am so sorry I haven’t had the time to read let alone appreciate, this very important report. It’s on my to do list.
    However, thank you very much for publicising another scandalous issue.


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